1. The History of Life

2.  The Big Bang occurred 13.7 billion years ago, creating the universe.

3.  4.6 billion years the solar system formed from a ball of gases called a nebula. – The oldest rocks on Earth are only 3.9 million years old!?!

4.  Earth’s early atmosphere contained –methane –ammonia –hydrogen –water vapor –maybe nitrogen

5. Conditions on Earth  High amount of UV radiation  Volcanoes  Meteorites  Extreme heat

6.  The oceans formed when water vapor condensed and fell to Earth.

7. SSSSimple organic compounds collected in the water and formed the building blocks of life.

8.  The simple organic compounds collected and reacted to form larger ones.  These were primitive “pre-cells”, large molecules with membrane-like structures around them.  Scientists have formed structures similar to “pre- cells” – microspheres and coacervates –These structures form spontaneously –Do not have genetic information –Display some properties of life

9.  3.5 billion years ago life appeared!  The 1 st organisms were anaerobic prokaryotic heterotrophs.  They obtained energy from the molecules in their environment.

10.  When food started to become scarce, organisms began to make their own food – autotrophs  Similar to archea  Use chemosynthesis to get food

11. AAAAround 3 billion years ago, photosynthetic organisms appeared. TTTThey produced oxygen and changed the Earth’s atmosphere. TTTThe Ozone layer was formed! –P–Provided protection from UV radiation and life could exist on land

12.  The O 2 in the atmosphere allowed aerobic respiration to occur. –This allowed more energy to be extracted from food molecules. –Allowed for greater complexity and prokaryotes diversified.

13.  Eukaryotic organisms appeared.  - Possibly from endosymbiosis. –Mutualistic relationship between primitive eukaryotic organisms and prokaryotes –How mitochondria and chloroplasts formed